1. Field of the Invention
The present invention relates to an automatic welding apparatus for welding pipes and large structures of various metal materials by non-consumable-electrode-type arc welding (TIG arc welding and transferred plasma-arc welding) and consumable-electrode-type arc welding (gas metal arc welding).
2. Description of the Related Art
TIG and plasma are typical conventional non-consumable-electrode-type arc sources. With conventional welding machines using such arc sources, welding is generally performed with a single filler metal wire. It is also the same practice with consumable-electrode-type welding, such as gas metal arc welding.
Although contributing to high-quality welding, conventional non-consumable-electrode-type and consumable-electrode-type arc welding machines can hardly be deemed as satisfactory in terms of production capacity. This is particularly so where changes in welding positions are involved, making it difficult to insure the requisite level of quality and production capacity.
While there is no particular problem in case of flat position welding, when welding fixed pipes or large structures which involves changes in welding position (e.g., overhead position), the molten pool gets bigger and tends to drip hampering improvement in production capacity.